1. Field of the Invention
This invention relates to cellular polyisocyanurates and intermediates therefor and especially to novel compatibilized homogeneous polyol (including diols) blends, and to their usage in a process for the making of such cellular products.
2. Description of the Prior Art
Cellular polyisocyanurates are well known in the art for use in thermal insulating applications and for their heat and flame resistance. Polyols are commonly added to the foam-forming composition (commonly called a resin blend or resin premix) to modify foam properties. When a fluorocarbon blowing agent is employed in the foam-forming composition, a problem in compatibility between the polyol (especially aromatic polyester polyols) and such fluorocarbon may arise in resin premixes.
As those skilled in the art appreciate, the preparation of homogeneous polyol blends, and resin precursor blends (which latter typically comprise such polyol blends, blowing agent, cell stabilizing surfactant, and trimerization catalyst) in the isocyanate polymerization art can involve multi-component mixtures. While sometimes a blend of different polyols present in a resin precursor blend can overcome fluorocarbon compatibility problems, characteristically when aromatic polyester polyols are used, such compatibility problems are believed to be difficult to overcome without using a compatibility agent.
Aromatic polyester polyols apparently cannot be blended with usable amounts of fluorocarbon blowing agents because of mutual insolubility characteristics causing incompatibility and nonhomogeneity in a resulting mixture. A compatibility agent in such a mixture produces compatibility (mutual solubility in effect) and homogeneity.
A class of amide diols is disclosed in U.S. Pat. No. 4,246,364 as being useful compatibility agents for such polyols and fluorocarbon blowing agents when material of such class is employed at the relatively high rate of from about 20 to 85 weight percent apparently on a 100 weight percent total polyol blend composition weight basis. Certain types of polyols, such as aromatic ester polyols, produced with low molecular weight aliphatic polyols, appear to be so incompatible with fluorocarbon blowing agents that, in a polyol blend containing such aromatic polyester polyols in relatively high percentages, large amounts of such an amide diol appear to be needed to achieve compatibility with fluorocarbon blowing agents. When such a large quantity of amide diol is employed, the cost of foam manufacture increases (because of the cost of the amide diol).
One class of aromatic polyester polyols which has heretofore been successfully employed in this art, and which is relatively incompatible with fluorocarbon blowing agents, but which is compatibilizable therewith by using an amide diol of the above referenced Koehler et al. U.S. Pat. No. 4,246,364, comprises reaction products of a low molecular weight polyether polyol, such as diethylene glycol, with poly(carbomethoxy-substituted) diphenyls and also benzyl esters. Such polyols are available commercially under the trademark "Terate" from ICI Americas, Inc. and "Urol" from UCT, Inc. Such diethylene glycol diphenyl and benzyl esters are commercially used at rates apparently ranging up to about 70 to 90 weight percent of a total polyol blend in making polyisocyanurate foam products. As a class, such "Terate" type polyol compositions are characteristically based on diphenyl esters, while another type of such aromatic ester polyol, the phthalate polyester polyols, are primarily based essentially on single aromatic substituted monophenyl ring structures.
This incompatibility effect appears to be particularly evident when it is desired to utilize phthalate ester polyols in relatively high percentages, but it is desirable to use such phthalate ester polyols in resin precursor systems because they apear to be appreciably less expensive than many prior art polyols which are suitable as reactants with isocyanates to produce polyisocyanurate foams.
Certain monofunctional hydroxyl terminated nonionic surfactants, such as, for example, polyethoxylated alkyl phenol nonionics that contain not more than about 15 moles of condensed ethylene oxide per molelucle and thus have molecular weights substantially below about 900 are believed to have been heretofore used as compatibility agents for polyol/fluorocarbon blowing agent resin precursor systems. These prior art nonionic compatibility agents contain substantially no propylene oxide. Particularly when formulating blends of phthalate ester polyols with fluorocarbon blowing agents, it appears to be necessary, in order to achieve the desired blend homogeneity, to use significantly high concentrations of such prior art nonionic surfactants for specified respective amounts of specified aromatic polyester polyols and fluorocarbon blowing agents which is undesirable not only from a cost standpoint, but also from a standpoint of degrading product foam properties, such as compressive strength. The property degradation can be so great as to make the product foams unusable and unsuitable for conventional commercial foam applications. This property deterioration is attributed in theory (and there is no intent to be bound herein by theory) to the circumstance that the monohydroxyl functionality of such surfactants makes them react as chain terminating components in the polyisocyanurate polymerization reaction, thereby producing excessive amounts of low molecular weight isocyanurate polymer which may result in such losses in product desirable properties.
Thus, there remains a need in the art for new and improved compatibility agents which will permit one to compatibilize polyols, especially aromatic polyester polyols, with fluorocarbon blowing agents and achieve complete blend homogeneity and solubilization without causing any substantial deterioration in product foam properties.